Knee-controlled motor control device for a motor-driven presser mechanism of a sewing machine

ABSTRACT

A motor control device is used to control an electric motor that drives a presser mechanism of a sewing machine and includes a knee lever mechanism and a control module. The knee lever mechanism includes a switch component, an actuator rotatable to actuate the switch component at a predetermined angular position, and a rotatable knee lever operable by knee contact to rotate and to drive rotation of the actuator. When the control module determines that the switch component is actuated, the control module controls the electric motor to move the presser mechanism to dispose a presser foot of the presser mechanism at a predetermined height relative to a bed of the sewing machine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a motor control device for a sewing machine, and more particularly to a knee-controlled motor control device for a motor-driven presser mechanism of a sewing machine.

2. Description of the Related Art

FIG. 1 shows a sewing machine 10 including a conventional knee-controlled presser driving device 1 adapted for controlling movement of a presser foot 11 of a presser mechanism. The conventional presser driving device 1 includes an attachment seat 12, a knee lever connector 13, a knee lever 14 and a cord component 15. The knee lever connector 13 is rotatably disposed on the attachment seat 12, and includes a connection portion 131 and a driving portion 132. The knee lever 14 is mounted to the knee lever connector 13 and is operable by knee contact to rotate and to drive rotation of the knee lever connector 13 relative to the attachment seat 12. The cord component 15 has two ends connected to the driving portion 132 of the knee lever connector 13, and the presser mechanism, respectively. When the knee lever 14 is rotated and drives rotation of the knee lever connector 13, the driving portion 132 in turn drives the presser mechanism, so as to result in vertical movement of the presser foot 11 through the cord component 15.

The conventional knee-controlled presser driving device 1 of the sewing machine 10 has the following drawbacks:

1. The movement of the presser foot 11 is driven through the cord component 15, and the movement precision of the presser foot 11 may be affected by physical property variation of the cord component 15, such as extension or shrinkage of the cord component 15 that may cause displacement differences between the two ends of the cord component 15 during rotation of the driving portion 132 of the knee lever connector 13, and that results in adverse effect on movement precision of the presser foot 11.

2. Installation and routing of the rope component 15 must be carefully considered, so as to ensure that the driving portion 132 of the knee lever connector 13 can smoothly drive the cord component 15, and thereby ensure proper movement of the presser foot 11.

In view of the above drawbacks, it has been proposed heretofore to use an electric motor for driving movement of the presser foot 11 of the presser mechanism instead of the cord component 15. In addition, the sewing machine usually has a separate mechanism to move and position the presser foot at a predetermined height for facilitating user's operation.

U.S. Pat. No. 8,161,897 discloses a sewing machine which uses a knee lever mechanism with a potentiometer to control operation of an electric motor that drives vertical movement of a presser foot. However, this patent does not disclose a mechanism for automatic movement of the presser foot to a predetermined height using the knee lever mechanism thereof.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a motor control device that is adapted for controlling an electric motor that drives movement of a presser mechanism of a sewing machine, and that is operable to dispose a presser foot of the presser mechanism at a predetermined height.

According to one aspect of the present invention, there is provided a motor control device for controlling operation of an electric motor that drives movement of a presser mechanism of a sewing machine. The motor control device comprises:

a knee lever mechanism including:

-   -   a switch component,     -   an actuator rotatable to actuate the switch component when         rotated to a predetermined angular position, and     -   a rotatable knee lever operable by knee contact to rotate and to         drive rotation of the actuator; and

a control module coupled to the switch component and to be coupled to the electric motor.

When the control module determines the switch component to be in an actuated state, the control module is configured to control operation of the electric motor to move the presser mechanism to dispose a presser foot of the presser mechanism at a predetermined height relative to a bed of the sewing machine.

Another object of the present invention is to provide a presser driving device for driving movement of a presser mechanism of a sewing machine.

According to another aspect of the present invention, a presser driving device comprises a knee lever mechanism, a control module coupled to the knee lever mechanism, and an electric motor coupled to the control module and to be coupled to the presser mechanism.

The knee lever mechanism includes:

-   -   a switch component coupled to the control module,     -   an actuator rotatable to actuate the switch component when         rotated to a predetermined angular position, and     -   a rotatable knee lever operable by knee contact to rotate and to         drive rotation of the actuator.

When the control module determines the switch component to be in an actuated state, the control module is configured to control operation of the electric motor to move the presser mechanism to dispose a presser foot of the presser mechanism at a predetermined height relative to a bed of the sewing machine.

Yet another object of the present invention is to provide a sewing machine that comprises:

a bed;

a head disposed above the bed;

a presser mechanism supported by the head and including a presser bar and a presser foot at one end of the presser bar; and

a presser driving device including a knee lever mechanism, a control module coupled to the knee lever mechanism, and an electric motor coupled to the presser mechanism and the control module.

The knee lever mechanism includes:

-   -   a switch component coupled to the control module,     -   an actuator rotatable to actuate the switch component when         rotated to a predetermined angular position, and     -   a knee lever mounted for rotation relative to the bed and         operated by knee contact to rotate and to drive rotation of the         actuator.

When the control module determines the switch component to be in an actuated state, the control module is configured to control operation of the electric motor to move the presser bar to dispose the presser foot at a predetermined height relative to the bed.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:

FIG. 1 is a schematic diagram showing a connection relationship of a conventional knee-controlled presser driving device and a presser foot in a sewing machine;

FIG. 2 is a schematic diagram showing a sewing machine that includes a preferred embodiment of the presser driving device according to the present invention;

FIG. 3 is a perspective view showing a rotary axle portion of a variable resistor component of the preferred embodiment at an initial angular position;

FIG. 4 is a side view of the preferred embodiment showing the rotary axle portion of the variable resistor component of the preferred embodiment at the initial angular position;

FIG. 5 is a perspective view showing the rotary axle portion of the variable resistor component of the preferred embodiment when being rotated;

FIG. 6 is a side view of the preferred embodiment showing an actuator of the preferred embodiment when rotated to a predetermined angular position; and

FIG. 7 is a block diagram showing a connection relationship of a control module of the preferred embodiment with other components in the sewing machine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 2, a sewing machine is shown to include a bed 100, a head 110 disposed above the bed 100, a presser mechanism 200 supported by the head 110, and a presser driving device including an electric motor 20 (such as a stepper motor) and the preferred embodiment of the motor control device according to this invention. The presser mechanism 200 includes a presser bar 21 and a presser foot 2 at one end of the presser bar 21. The motor control device is adapted for controlling operation of the electric motor 20 that drives movement of the presser mechanism 200 of the sewing machine, and includes a knee lever mechanism 3, a limiting module 4 and a control module 5 (see FIG. 7).

Referring to FIG. 3 and FIG. 4, the knee lever mechanism 3 includes an attachment seat 31, a knee lever 32, an actuator 33, a variable resistor component 34 disposed on the attachment seat 31, a switch component 35 disposed on the attachment seat 31, and a first spring 36.

The knee lever 32 is mounted for rotation relative to the bed 100 and is operated by knee contact to rotate.

The actuator 33 is mounted rotatably to the attachment seat 31 and has a lever-connecting portion 331 connected to the knee lever 32 for co-rotation with the knee lever 32 relative to the attachment seat 31, and a driving portion 332 opposite to the lever-connecting portion 331. The actuator 33 is disposed between the switch component 35 and the variable resistor component 34 with the lever-connecting portion 331 disposed adjacent to the switch component 35 and the driving portion 332 disposed adjacent to the variable resistor component 34. The actuator 33 is formed with a protrusion 333 disposed to actuate the switch component 35 when the actuator 33 is rotated to a predetermined angular position.

The variable resistor component 34 has a rotary axle portion 341, a forced portion 342 that extends from the rotary axle portion 341 and that abuts against the driving portion 332 of the actuator 33, and a protrusion part 343 extending from the rotary axle portion 341 in a direction opposite to the forced portion 342, and has a resistance varying with rotation of the rotary axle portion 341. Referring to FIG. 5, the forced portion 342 is forced by rotation of the actuator 33 so as to rotate the rotary axle portion 341 and vary the resistance of the variable resistor component 34, and further rotation of the actuator 33 to the predetermined angular position results in the protrusion 333 of the actuator 33 actuating the switch component 35, as shown in FIG. 6.

The first spring 36 has opposite ends that are connected to the attachment seat 31 and the actuator 33, respectively, so as to provide a resilient force to stabilize rotation of the actuator 33.

The limiting module 4 includes a base seat 41, a limiting member 42, and a second spring 43.

The base seat 41 is disposed on the attachment seat 31 and adjacent to the rotary axle portion 341. The limiting member 42 is disposed on the base seat 41 and has an end portion disposed to abut against an edge of the rotary axle portion 341 of the variable resistor component 34 when the rotary axle portion 341 is at an initial angular position relative to the base seat 41, as shown in FIGS. 3 and 4.

The second spring 43 has opposite ends connected to the protrusion part 343 and the base seat 41, respectively. The second spring 43 provides a resilient force to bias the rotary axle portion 341 to the initial angular position.

Referring to FIG. 7, the control module 5 is electrically coupled to the variable resistor component 34, the switch component 35 and the electric motor 20. The control module 5 is a programmable module that is configured with a built-in program 51 to perform conversion of a resistance variation of the variable resistor component 34 into a displacement value of the presser foot 2. For example, a relationship between resistance increment or decrement of the variable resistor component 34 and the movement direction of the presser foot 2, and a relationship between the resistance variation of the variable resistor component 34 and the displacement value of the presser foot 2 may be user-defined through the built-in program 51. When the control module 5 determines the switch component 35 to be in a non-actuated state, the control module 5 is configured to control operation of the electric motor 20 to move the presser mechanism 200 according to the converted displacement value of the presser foot 2. When the control module 5 determines the switch component 35 to be in an actuated state, the control module 5 is configured to control operation of the electric motor 20 to move the presser mechanism 200 to dispose the presser foot 2 of the presser mechanism 200 at a predetermined height relative to the bed 100 of the sewing machine.

To sum up, the motor control device of this invention uses the knee lever 32 to vary resistance of the variable resistor component 34, so as to control the electric motor 20 to drive movement of the presser foot 2. Through the switch component 35 and the protrusion 333, the presser foot 2 may be disposed at the predetermined height using the knee lever 32.

While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

What is claimed is:
 1. A motor control device for controlling operation of an electric motor that drives movement of a presser mechanism of a sewing machine, said motor control device comprising: a knee lever mechanism including: a switch component, an actuator rotatable to actuate said switch component when rotated to a predetermined angular position, and a rotatable knee lever operable by knee contact to rotate and to drive rotation of said actuator; and a control module coupled to said switch component and to be coupled to the electric motor; wherein, when said control module determines said switch component to be in an actuated state, said control module is configured to control operation of the electric motor to move the presser mechanism to dispose a presser foot of the presser mechanism at a predetermined height relative to a bed of the sewing machine.
 2. The motor control device as claimed in claim 1, wherein said knee lever mechanism further includes a variable resistor component coupled to said control module, spaced apart from said switch component, having a rotary axle portion, and a forced portion that extends from said rotary axle portion and that abuts against said actuator, and having a resistance varying with rotation of said rotary axle portion, wherein rotation of said actuator forces said forced portion so as to rotate said rotary axle portion and vary the resistance of said variable resistor component; wherein further rotation of said actuator to the predetermined angular position results in said actuator actuating said switch component; and wherein, when said control module determines said switch component to be in a non-actuated state, said control module is configured to control operation of the electric motor to move the presser mechanism according to the resistance of said variable resistor component.
 3. The motor control device as claimed in claim 2, wherein said knee lever mechanism further includes an attachment seat, said actuator being mounted rotatably to said attachment seat and having a lever-connecting portion connected to said knee lever for co-rotation with said knee lever relative to said attachment seat, and a driving portion opposite to said lever-connecting portion and abutting against said forced portion of said variable resistor component.
 4. The motor control device as claimed in claim 3, wherein said actuator is disposed between said variable resistor component and said switch component, said variable resistor component being disposed adjacent to said driving portion, said switch component being disposed adjacent to said lever-connection portion.
 5. The motor control device as claimed in claim 4, wherein said actuator is formed with a protrusion disposed to actuate said switch component when said actuator is rotated to the predetermined angular position.
 6. The motor control device as claimed in claim 4, wherein said switch component and said variable resistor component are disposed on said attachment seat.
 7. The motor control device as claimed in claim 3, wherein said knee lever mechanism further includes a first spring having opposite ends that are connected to said attachment seat and said actuator, respectively.
 8. The motor control device as claimed in claim 7, wherein said variable resistor component further has a protrusion part extending from said rotary axle portion, said knee lever mechanism further including a limiting module that includes: a base seat disposed on said attachment seat and adjacent to said rotary axle portion; a limiting member disposed on said base seat and having an end portion disposed to abut against said rotary axle portion of said variable resistor component when said rotary axle portion is at an initial angular position relative to said base seat; and a second spring having opposite ends connected to said protrusion part and said base seat, respectively, said second spring biasing said rotary axle portion to the initial angular position.
 9. The motor control device as claimed in claim 3, wherein said rotary component further has a protrusion part extending from said rotary axle portion, said knee lever mechanism further including a limiting module that includes: a base seat disposed on said attachment seat and adjacent to said rotary axle portion; a limiting member disposed on said base seat and having an end portion disposed to abut against said rotary axle portion of said variable resistor component when said rotary axle portion is at an initial angular position relative to said base seat; and a spring having opposite ends connected to said protrusion part and said base seat, respectively, said spring biasing said rotary axle portion to the initial angular position.
 10. The motor control device as claimed in claim 2, wherein, when said control module determines said switch component to be in the non-actuated state, said control module is configured to convert a resistance variation of said variable resistor component into a displacement value of the presser foot, and to control operation of the electric motor for moving the presser mechanism according to the displacement value.
 11. The motor control device as claimed in claim 10, wherein said control module is a programmable module that is configured with a built-in program to perform conversion of the resistance variation of said variable resistor component into the displacement value of the presser foot.
 12. A presser driving device for driving movement of a presser mechanism of a sewing machine, said presser driving device comprising a knee lever mechanism, a control module coupled to said knee lever mechanism, and an electric motor coupled to said control module and to be coupled to the presser mechanism; wherein said knee lever mechanism includes: a switch component coupled to said control module, an actuator rotatable to actuate said switch component when rotated to a predetermined angular position, and a rotatable knee lever operable by knee contact to rotate and to drive rotation of said actuator; wherein, when said control module determines said switch component to be in an actuated state, said control module is configured to control operation of said electric motor to move the presser mechanism to dispose a presser foot of the presser mechanism at a predetermined height relative to a bed of the sewing machine.
 13. A sewing machine comprising: a bed; a head disposed above said bed; a presser mechanism supported by said head and including a presser bar and a presser foot at one end of said presser bar; and a presser driving device including a knee lever mechanism, a control module coupled to said knee lever mechanism, and an electric motor coupled to said presser mechanism and said control module; wherein said knee lever mechanism includes: a switch component coupled to said control module, an actuator rotatable to actuate said switch component when rotated to a predetermined angular position, and a knee lever mounted for rotation relative to said bed and operated by knee contact to rotate and to drive rotation of said actuator; wherein, when said control module determines said switch component to be in an actuated state, said control module is configured to control operation of said electric motor to move said presser bar to dispose said presser foot at a predetermined height relative to said bed. 